Control device for working vehicle

Abstract

The invention provides a control system for a working vehicle, which can realize higher work performance and better fuel economy in a compatible way. A controller 10 includes table 10 a , 10 b and tables 10 e , 10 f for deciding maximum pump absorption torques and engine output torques based on an engine revolution speed, and selectors 10 c , 10 g for switching over the decided maximum pump absorption torques and engine output torques depending on a work performance mode or a fuel economy mode is selected. A pump absorption torque characteristic for the fuel economy mode is set so as to provide a relative small maximum pump absorption torques TB in a high revolution range, and an engine output characteristic for the fuel economy mode is set so as to provide a relatively small engine output torque in the high revolution range.

1. A control system for a working vehicle comprising an engine, a travel pedal for instructing a target revolution speed of said engine, a fuel injector for controlling a fuel injection amount depending on the target revolution speed of the engine thereby to control an output torque and revolution speed of said engine, a transmission for traveling including a torque converter which is driven by said engine, a variable displacement hydraulic pump driven by said engine, and a hydraulic actuator driven by a hydraulic fluid delivered from said hydraulic pump, and first pump torque control means for controlling an absorption torque of said hydraulic pump not to exceed a maximum absorption torque, wherein said control system comprises:
 switching-over means; 
 engine torque control means for selecting one of at least two preset engine output characteristics with respect to an engine revolution speed in response to an instruction from said switching-over means, determining a maximum fuel injection amount corresponding to the engine revolution speed at the current time in accordance with the selected engine output characteristic, and controlling said fuel injector such that the fuel injection amount controlled depending on the target revolution speed of the engine does not exceed said maximum fuel injection amount, thereby controlling the output torque of said engine; and 
 second pump torque control means for selecting one of at least two preset pump absorption torque characteristics with respect to an engine revolution speed in response to the instruction from said switching-over means and determining a maximum absorption torque corresponding to the engine revolution speed at the current time in accordance with the selected pump absorption torque characteristic, thereby controlling the maximum absorption torque of said hydraulic pump; and 
 said switching-over means is a switch for instructing one of a work performance mode and a fuel economy mode; 
 said engine torque control means selects the output torque characteristic providing, in the fuel economy mode, a slightly smaller engine output torque in a relatively high range of the engine revolution speed than that in the work performance mode; and 
 said second pump torque control means selects the pump absorption torque characteristic providing, in the fuel economy mode, a slightly smaller maximum pump absorption torque in the relatively high range of the engine revolution speed than that in the work performance mode corresponding to a reduction of the engine output torque made by said engine torque control means. 
 
   
   
     2. The control system for the working vehicle according to  claim 1 , wherein said engine torque control means sets, as the engine output characteristic, an engine output torque characteristic with respect to the engine revolution speed and determines an engine output torque corresponding to the engine revolution speed at the current time in accordance with the selected engine output torque characteristic, and then converts the determined engine output torque into said maximum fuel injection amount. 
   
   
     3. The control system for the working vehicle according to  claim 1 , wherein said engine torque control means sets, as the engine output characteristic, a fuel injection amount characteristic with respect to the engine revolution speed and determines a fuel injection amount corresponding to the engine revolution speed at the current time, and then uses the determined fuel injection amount as said maximum fuel injection amount.